=(8+2x/25)(400-x)
=3200+32x-8x-2x? /25
=-2x? /25+24x+3200
2、4800=-2x? /25+24x+3200
x? -300x+20000=0
(x-200)(x- 100)=0
x=200 x= 100
According to the meaning of the question
x=200
3、y=-2x? /25+24x+3200
=-2/25(x? -300 times +22500)+5000
=-2/25(x- 150)? +5000
∴x= 150 has a maximum value, and the maximum value is 5000.